How do you lower nitrite and nitrate levels for a newly set-up African cichlid tank also what are the optimum hardness and alkilinity levels for said tank?

The only safe way to lower Nitrite levels is to have a properly cycled filter doing the job bacteriologically for you. As far as keeping the resultant Nitrates down that can only be achieved by either using them up by growing plants or changing heaps of water every week. Recommended levels. pH around 8.5 to 9. GH more than 20 ppm